The X-Ray Variability Properties of PG Quasars: New ROSAT/HRI Results

Abstract

While X-ray variability in Seyfert galaxies has been the subject of intensive study (see review by Mushotzky, Done & Pounds 1993, and Green et al 1993), the variability of quasars, which are fainter, received far less attention (the Zamorani et al. study of 1984 remains the most extensive to date), despite the fact that X-ray variability is common in quasars. The X-ray emission most likely originates in the innermost regions of quasar, and so its variability can unravel the basic parameters of the quasar central engine (mass, geometry, radiation mechanisms, radiative transfer) none of which are yet well constrained.